In Psychology, all roads lead to Ancient Greece. The discipline of Industrial-Organizational (I-O) Psychology can trace its roots to Plato’s The Republic when he classifies citizens into guardians, auxiliaries and workers and gives selection and training advice (Katzell & Austin, 1992). In the book of Exodus, Moses sought advice on how to organize the ancient Israelis (Katzell & Austin, 1992). The study and employment of I-O Psychology principles similar to those used today however, really began in the early 1900s (Katzell & Austin, 1992).
Hugo Munsterberg, a professor at Harvard, began to apply psychology to industry in the early 1900s. In 1913 he published Psychology and Industrial Efficiency in which he wrote that industrial efficiency could be achieved by finding the “best man” for “the best work” for “the best possible effect” (Munsterberg, 1922, p. 426). Munsterberg, a German, came into disfavor because of World War I, however this war gave a major boost to I-O Psychology. One of Munsterberg’s well known endeavors was to help identify women who would make good switchboard operators through a series of tests of memory, attention and accuracy of movement (Munsterberg, 1922). Cattell, Walter Dill Scott and Walter Van dyke Bingham were also involved in employee selection and training research (Landy & Conte, 2010). Many of these psychologists moved into applied psychology in the workplace usually at the request of businesses (Katzell & Austin, 1992).

In World War I, psychologists were used to test military personnel for many things including officer potential (Katzell & Austin, 1992). In the 1930s, focus on finding the “right person” turned to a focus on the environment with the famous Hawthorne studies in which productivity initiatives brought to light the effect being a part of a research project can have on employees.
Lewin studied leadership and the effect on productivity (Katzell & Austin, 1992). Legislation such as the Civil Rights Act contributed to the developmental of the discipline of I-O Psychology as tests used in employment were mandated to undergo more rigorous validity and reliability testing (Landy & Conte, 2010).
In Landy and Conte (2010) I-O Psychology is defined as the “application of psychological principles, theory and research to the work setting” (p. 8). These authors expand the scope of I-O Psychology to the study of family, culture, legislation and world events as all of these may have an effect on the individual worker and the organizations they work for (Landy & Conte, 2010).

In terms of the American Psychological Association (APA) the scientific and professional organization of psychologists in the United States, there was a history of variation between the counseling psychologists and the applied psychologists in terms of research and roles. In 1937 Applied Psychology became an APA division and I-O Psychology was a subset until becoming its own division in 1947. Division 14 was initially called Industrial and Business Psychology; changed to Industrial Psychology in 1962 and finally became Industrial Organizational Psychology in 1973 (Koppes, 2009).

When I-O Psychology was in its infancy Munsterberg wrote that “Industrial Psychology would benefit workers as well as employers” (Katzell & Austin, 1992). A brief scan of current I-O related articles in the Academic Search Premier Database includes topics such as writing recommendations, hiring, real time performance monitoring, job satisfaction in nurse managers, predicting leadership in military settings, improving KSAO (knowledge, skill, aptitude and other) ratings, creating norms for global talent management, using human factors to assess mistakes, and the effect of workaholism on job satisfaction, family, and leisure activities. These show the far reaching scope of practice in the application of psychological principles to the workplace